Abstract
Background Proteinuria is an important marker of kidney disease. Protein-creatinine ratio and protein-osmolality ratio in a spot urine sample have been proposed as alternatives to 24-hour urinary protein excretion, to simplify sample collection and minimize errors due to incorrect sample collection. Objective Study was to compare validity of urine protein-osmolality ratio and urine protein-creatinine ratio in a random urine sample against 24-hour urinary protein excretion, to detect proteinuria in a paediatric population. Methods A cross sectional descriptive study was conducted by recruiting 85 children with kidney disease from medical wards and nephrology clinic at Lady Ridgeway Hospital, as well as, 56 healthy children aged 3-12 years. Twenty four-hour urine samples and spot urine samples were collected from each participant. Urine protein-osmolality ratio and urine protein-creatinine ratio in the spot urine sample were determined and compared with 24-hour urinary protein excretion. Data was analysed using SPSS statistical package. Standard descriptive methods (mean, median, standard deviation etc.) were used to describe the measured parameters. Receiver Operator Characteristic (ROC) curves were created using protein-osmolality ratio and protein-creatinine ratio as test variables, and 24-hour urinary protein excretion as the ‘gold standard’ variable. Optimum cut of values, maximizing sensitivity and specificity, for protein-osmolality ratio and protein-creatinine ratio was determined using ROC curves. Results The optimal value discriminating normal from abnormal protein excretion was determined to be a protein-osmolality ratio of 0.38 mg/L: mOsm/kgH 2 O (sensitivity 85.7%, specificity 100%) and a protein-creatinine ratio of 28 mg/mmol (sensitivity 100%, specificity 94%). The cutoff value for discriminating mild from nephrotic proteinuria was to be a protein-osmolality ratio of 2.00 mg/L: mOsm/kgH 2 O (sensitivity 91.5%, specificity 100%) and a protein-creatinine ratio of 186 mg/mmol (sensitivity 93%, specificity 98.5%). Conclusions Both urine protein-creatinine ratio and urine protein-osmolality ratio can be used to determine nephrotic proteinuria. Urine protein-creatinine ratio was more sensitive than urine protein-osmolality ratio in detecting mild proteinuria from normal proteinuria.
Highlights
Proteinuria is an early and sensitive marker of kidney damage in many types of chronic kidney disease[1]
The recent National Kidney Foundation Kidney Disease Outcome Quality Initiative (K/DOQI) clinical practice guideline for kidney disease has recommended the use of protein-creatinine ratio in an untimed spot urine specimen, for the assessment of kidney damage and monitoring of proteinuria, in patients with renal disease except in post pubertal children with diabetes mellitus[1].In addition, protein-osmolality ratio in a random urine sample has been suggested as another tool for the assessment of renal disease
Data describing the protein-osmolality ratios of normal population and in patients with proteinuria have been published for adults as well as for children
Summary
Proteinuria is an early and sensitive marker of kidney damage in many types of chronic kidney disease[1]. Estimates of proteinuria in monitoring kidney disease are useful in predicting the progression of renal damage and evaluating response to therapy. Quantification of urinary protein excretion is an important part of a nephrological evaluation[1]. Most definitive and reliable method for quantification of proteinuria is by assessing 24-hour urinary protein excretion[1]. Incorrect volume of urine collection may be associated with over or underestimation of proteinuria. Proteinuria is an important marker of kidney disease. Protein-creatinine ratio and proteinosmolality ratio in a spot urine sample have been proposed as alternatives to estimation of 24-hour urinary protein excretion in order to simplify sample collection and minimize errors due to incorrect sample collection
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